A thermal printer prints images by transferring donor material from a donor ribbon onto a receiver medium. Typically, this is done by selectively heating the donor ribbon to melt donor material while concurrently pressuring the donor ribbon against the receiver medium. In this way, melted donor material transfers from the donor ribbon to the receiver medium to form an image while unmelted donor material remains on the donor ribbon. Upon initial transfer to the receiver medium, donor material is often liquid and hot. Within a short period of time, the donor material enters a transition or glassy state. After a longer period of time, the donor material solidifies forming a permanent record on the receiver medium. The donor ribbon and receiver medium are separated after transfer of the material to yield a receiver medium having a pattern of deposited donor material forming an image.
Donor ribbon is typically connected between a supply spool, which initially carries a supply of unused donor ribbon, and a take-up spool upon which used donor ribbon is wound. In operation, the take-up spool is rotated to draw donor ribbon from the supply spool and across the print head for use in printing.
Often the donor spool and take-up spool are joined together by a structural framework to form a thermal donor cartridge. This structural framework positions the supply spool and the take-up spool in a preferred geometric relationship to facilitate proper loading and can also be used to provide surfaces that enclose or otherwise protect the donor ribbon from damage due to incidental contact and from damage due to exposure to contaminants.
It will be appreciated that there are a wide variety of thermal printers that use thermal donor cartridges. Typically, each donor cartridge is adapted for use in one specific thermal printer. Accordingly, there are a wide variety of donor cartridges. For example, the conveyance system used to position the receiver medium can take any of several different forms depending on the type of printer. Some thermal printers use dual pinch roller receiver systems that enable a compact printer to create an image without white borders on the print. Other thermal printers use channel systems to move receiver medium during printing. Such channel systems enable an extremely low cost printer. Still other thermal printers use drum systems to move receiver medium during printing. Such drum systems have the potential for good color registration yet at a fairly large size on the desktop.
Thermal printers that use donor cartridges typically provide for printhead articulation so as to allow the printhead to be moved to a secure location during loading and unloading of the donor cartridge. Here too, a variety of approaches can be used to provide such printhead articulation. For example, small pivot head arms typically mate with drum type thermal printer systems while a long lever arm that pivots outside the distance of the spools is often used in roller receiver systems. Accordingly, the design of a thermal donor cartridge will typically be adapted to reflect this. Additional considerations and accommodations are made in thermal printer cartridges to facilitate the movement of donor ribbon so as to minimize donor ribbon wrinkle and other related problems.
Further, there are significant differences in the way in which donor ribbon is used in thermal printers. More specifically, many thermal printers are designed to separate donor ribbon from the receiver medium while the donor material is hot and is still in a liquid or molten state while other thermal printers separate the donor ribbon from the receiver medium only after the receiver medium has cooled for example to a solidified state. However, the donor cartridges that are designed for use in thermal printers that separate the donor web from the receiver medium while the donor material is hot are typically not compatible with donor cartridges that are designed for use in thermal printers that separate the donor web from the receiver medium when the donor material has cooled. Largely, this is because the latter printers require donor cartridges that are sized and shaped to allow the donor ribbon and receiver medium to travel in concert after printing to allow for cooling while the former printers separate the donor ribbon from the receiver medium soon after printing.
Because of these differences in thermal printers, a thermal donor cartridge is typically adapted for use in one printer and is rarely useful in different thermal printers. Accordingly, it is also known to provide donor ribbon in the form of a matched pair of donor spools and take-up spools that are joined only by the donor ribbon. Such an arrangement of donor ribbon allows the donor ribbon to be used in a variety of different printers in that the take-up and supply spools can be positioned at any distance relative to each other and in that such an arrangement imposes no inherent limitations on the path that the donor ribbon must take as it passes from the supply spool to the take-up spool. However, a person installing such donor ribbon in a thermal printer must exercise skill in handling and loading the donor ribbon to ensure that the spools and the donor ribbon are properly threaded through the donor ribbon travel path in the printer and must also use a care to ensure that the donor ribbon is not damaged, altered or contaminated.
What is needed in the art therefore is a low cost thermal printer cartridge that can be used with a wide variety of thermal printers.